19-3169; Rev 0; 1/04
Power-Source Selector for
Dual-Battery Systems
General Description
The MAX1538 selector provides power-source control
for dual-battery systems. The device selects between
an AC adapter and dual batteries based on the pres-
ence of the three power sources and the state of
charge of each battery. The MAX1538 includes analog
comparators to detect AC/airline-adapter presence and
determine battery undervoltage. Fast analog circuitry
allows the device to switch between power sources to
implement a break-before-make time, which allows hot
swapping of battery packs. The MAX1538 indepen-
dently performs power-source monitoring and selec-
tion, freeing the system power-management µP for
other tasks. This simplifies the development of µP
power-management firmware and allows the µP to enter
standby, reducing system power consumption.
The MAX1538 supports “relearn mode,” which allows
the system to measure and fully utilize battery capacity.
In this state, the part allows the selected battery to be
discharged even when an AC adapter is present. The
MAX1538 can also be used to power the system in an
aircraft. On detecting an airline adapter, the MAX1538
automatically disables charging or discharging of bat-
tery packs and only allows the system to be powered
from the adapter.
The MAX1538 is available in a space-saving 28-pin thin
QFN package with a maximum footprint of 5mm x 5mm.
Features
♦
Automatically Detects and Responds to
Low-Battery Voltage Condition
Battery Insertion and Removal
AC-Adapter Presence
Airline-Adapter Presence
♦
Step-Down and Step-Up Charger Compatibility
♦
Fast Break-Before-Make Selection
Allows Hot Swapping of Power Sources
No External Schottky Diodes Needed
♦
50µA Maximum Battery Quiescent Current
♦
Implements Battery Capacity Relearning
♦
Allows Usage of Aircraft Supply
♦
Direct Drive of P-Channel MOSFETs
♦
Simplifies Power-Management µP Firmware
♦
4.75V to 28V AC-Adapter Input Voltage Range
♦
Small 28-Pin Thin QFN Package (5mm x 5mm)
MAX1538
Ordering Information
PART
MAX1538ETI
TEMP RANGE
-40°C to +85°C
PIN-PACKAGE
28 Thin QFN
Typical Operating Circuit
SYSTEM LOAD
ADAPTER
Applications
Notebook and Subnotebook Computers
Internet Tablets
Dual-Battery Portable Equipment
ACDET
AIRDET
ADPIN
REVBLK
EXTLD
BATTERY
CHARGER
CHG_OUT
CHGIN
CHRG
BATSEL
RELRN
OUT2
OUT1
OUT0
MAX1538
ADPBLK
V
DD
Pin Configuration appears at end of data sheet.
MINVA
CHGA
CHGB
DISB
GND
DISA
BATB
BATA
BATTERY B
BATTERY A
BATSUP
MINVB
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
Power-Source Selector for
Dual-Battery Systems
MAX1538
ABSOLUTE MAXIMUM RATINGS
V
EXTLD
, V
BATSUP
, V
ADPIN
, V
BATA
, V
BATB
,
V
CHGIN
to GND .................................................-0.3V to +30V
V
ADPPWR
to GND...................................-0.3V to (V
ADPIN
+ 0.3V)
V
REVBLK
, V
ADPBLK
to GND ...................-0.3V to (V
EXTLD
+ 0.3V)
V
CHGA
, V
CHGB,
V
DISBAT
to GND ..........-0.3V to (V
CHGIN
+ 0.3V)
V
DISA
to GND..........................................-0.3V to (V
BATA
+ 0.3V)
V
DISB
to GND..........................................-0.3V to (V
BATB
+ 0.3V)
V
DD
, V
CHRG
, V
BATSEL
, V
RELRN
, V
OUT0
, V
OUT1
, V
OUT2
,
V
MINVA
, V
MINVB
, V
AIRDET
, V
ACDET
to GND..........-0.3V to +6V
Continuous Power Dissipation (T
A
= +70°C)
28-Pin Thin QFN 5mm x 5mm
(derate 20.8mW/°C above +70°C) ..........................1666.7mW
Operating Temperature Range
MAX1538ETI ....................................................-40°C to +85°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(V
BATA
= V
BATB
= V
CHGIN
= 16.8V, C
VDD
= 1µF, V
MINVA
= V
MINVB
= 0.93V, V
EXTLD
= V
ADPIN
= 28V, V
CHRG
= V
BATSEL
= V
RELRN
= 0,
C
ADPPWR
= C
REVBLK
= C
ADPBLK
= C
DISBAT
= C
DISA
= C
DISB
= C
CHGA
= C
CHGB
= 4.7nF,
TA = 0°C to +85°C,
unless otherwise noted.
Typical values are at T
A
= +25°C.)
PARAMETER
ADPIN, EXTLD Supply Voltage
Range
CHGIN, BATA, BATB and
BATSUP Supply Voltage Range
V
ADPIN
= highest,
V
ADPPWR
= high
V
ADPIN
= highest,
V
ADPPWR
= low
V
BATA
= highest,
V
DISA
= high
V
BATA
= highest, V
DISA
= low
V
BATB
= highest,
V
DISB
= high
V
BATB
= highest, V
DISB
= low
V
BATSUP
= highest
ADPIN Quiescent Current (ADPIN
Current When Not the Highest
Voltage)
BATA Quiescent Current (BATA
Current When Not the Highest
Voltage)
BATB Quiescent Current (BATB
Current When Not the Highest
Voltage)
EXTLD Quiescent Current
V
ADPIN
= 4.75V to 18V,
no external load at V
DD
V
BATA
= 4.75V to 19V,
no external load at V
DD
V
BATB
= 4.75V to 19V,
no external load at V
DD
V
ADPPWR
= high
V
ADPPWR
= low
V
DISA
= high
V
DISA
= low
V
DISB
= high
V
DISB
= low
CONDITIONS
MIN
4.75
4.75
21
23
21
24
21
24
18
0.01
2.6
3.9
7.0
3.9
7.0
3.0
0.02
0.03
3.1
6.1
TYP
MAX
28.00
19.00
50
54
42
50
42
50
40
0.5
µA
6
6.0
µA
12
6.0
µA
12
6.1
1.0
1.5
6.2
12.1
µA
µA
UNITS
V
V
ADPIN, BATA, BATB, BATSUP
Quiescent Current (Current from
the Highest Voltage Supply)
V
BATA
= 4.75V to 19V,
V
BATB
= 4.75V to 19V,
V
BATSUP
= 4.75V to 19V,
V
ADPIN
= 4.75V to 28V,
no external load at V
DD
µA
Adapter selected (REVBLK or ADPBLK pins low)
Adapter not selected (REVBLK and ADPBLK pins high)
AC or airline state (CHGA, CHGB, and DISBAT pins high)
Charge state (CHGA or CHGB pin low, DISBAT pin high)
Discharge or relearn state (CHGA or CHGB pin low,
DISBAT pin low)
CHGIN Quiescent Current
2
_______________________________________________________________________________________
Power-Source Selector for
Dual-Battery Systems
ELECTRICAL CHARACTERISTICS (continued)
(V
BATA
= V
BATB
= V
CHGIN
= 16.8V, C
VDD
= 1µF, V
MINVA
= V
MINVB
= 0.93V, V
EXTLD
= V
ADPIN
= 28V, V
CHRG
= V
BATSEL
= V
RELRN
= 0,
C
ADPPWR
= C
REVBLK
= C
ADPBLK
= C
DISBAT
= C
DISA
= C
DISB
= C
CHGA
= C
CHGB
= 4.7nF,
TA = 0°C to +85°C,
unless otherwise noted.
Typical values are at T
A
= +25°C.)
PARAMETER
LINEAR REGULATOR
V
DD
Output Voltage
V
DD
Power-Supply Rejection
Ratio
V
DD
Undervoltage Lockout
COMPARATORS
ACDET, AIRDET Input Voltage
Range
ACDET, AIRDET Input Bias
Current
ACDET, AIRDET Trip Threshold
ACDET, AIRDET Hysteresis
MINV_ Operating Voltage Range
MINV_ Input Bias Current
BAT_ Minimum Voltage Trip
Threshold
BAT_ Minimum Voltage
Hysteresis
BAT_ Pack Removal Detection
Threshold
BAT_ Pack Removal Hysteresis
GATE DRIVERS
(Note 1)
ADPPWR, REVBLK, ADPBLK,
DISBAT, DISA, DISB, CHGA,
CHGB Source Current (PMOS
Turn-Off)
ADPPWR, REVBLK, ADPBLK,
DISBAT, DISA, DISB, CHGA,
CHGB Sink Current (PMOS
Turn-On)
ADPPWR, REVBLK, ADPBLK,
DISBAT, DISA, DISB, CHGA,
CHGB Turn-On Clamp Voltage
(V
PIN
to V
SOURCE
)
V
SOURCE
= 15V, V
PIN
= 7.5V
V
SOURCE
= 15V, V
PIN
= 13V
V
SOURCE
= 15V, V
PIN
= 15V
V
SOURCE
= 15V, V
PIN
= 9.5V
V
SOURCE
= 8V to 19V (ADPPWR, REVBLK, and AOPBLK,
V
SOURCE
= 8V to 28V)
V
SOURCE
= 4.75V to 8V
18
3
20
10
-11.0
-8.00
60
mA
15
70
mA
55
-9.0
-7.0
V
-3.65
V
BAT_
falling
1.90
V
MINV_
= 0.93V to 2.6V
V
MINV_
= 0.93V
V
BAT_
falling
V
MINV_
= 1.5V
V
MINV_
= 2.6V
0.93
-50
4.605
7.455
12.93
4.65
7.5
13
125
2.0
85
2.10
V
AIRDET
= V
ACDET
= 3V
Input falling
1.97
0
0.1
2.0
20
2.60
+50
4.695
7.545
13.07
mV
V
mV
V
5.5
1
2.03
V
µA
V
mV
V
nA
I
VDD
= 0 to 100µA
V
BATA
or V
BATB
= 5V to 19V, V
ADPIN
= 5V
V
BATA
= V
BATB
= 5V, V
ADPIN
= 5V to 28V
V
BATA
, V
BATB
, or V
ADPIN
= 5V to 19V, sawtooth at
10V/µs, other supplies = 12V
Rising edge, relative to regulation point
-55
1
-10
mV
3.270
3.3
3.330
1.0
1.0
mV / V
V
CONDITIONS
MIN
TYP
MAX
UNITS
MAX1538
_______________________________________________________________________________________
3
Power-Source Selector for
Dual-Battery Systems
MAX1538
ELECTRICAL CHARACTERISTICS (continued)
(V
BATA
= V
BATB
= V
CHGIN
= 16.8V, C
VDD
= 1µF, V
MINVA
= V
MINVB
= 0.93V, V
EXTLD
= V
ADPIN
= 28V, V
CHRG
= V
BATSEL
= V
RELRN
= 0,
C
ADPPWR
= C
REVBLK
= C
ADPBLK
= C
DISBAT
= C
DISA
= C
DISB
= C
CHGA
= C
CHGB
= 4.7nF,
TA = 0°C to +85°C,
unless otherwise noted.
Typical values are at T
A
= +25°C.)
PARAMETER
ADPPWR, REVBLK, ADPBLK,
DISBAT, DISA, DISB, CHGA,
CHGB Turn-On Time
ADPPWR, REVBLK, ADPBLK,
DISBAT, DISA, DISB, CHGA,
CHGB Turn-Off Time
STATE SELECTION INPUTS
CHRG, BATSEL, RELRN Input
Low Voltage
CHRG, BATSEL, RELRN Input
High Voltage
CHRG, BATSEL, RELRN Input
Leakage Current
STATE OUTPUTS
OUT0, OUT1, OUT2 Sink Current
OUT0, OUT1, OUT2 Leakage
Current
TRANSITION TIMES
MINV_ Comparator Delay
AIRDET and ACDET Comparator
Delay
BAT_ Removal Comparator Delay
Battery-Insertion Blanking Time
State-Machine Delay
MOSFET Turn-On Delay
t
TRANS
5
t
BBLANK
t
MINV
t
ADP
V
BAT
_ = 5.5V to V
BAT
_ = 4.45V
Falling edge with -20mV overdrive
Falling edge with -20mV overdrive
13
5.5
2.7
10
21
50
7.5
10
31
11
6.0
µs
µs
µs
ms
ns
µs
V
OUT_
= 5.5V
V
OUT_
= 0.4V
V
OUT_
= 5.5V
1
25
0.1
1
mA
µA
V
CHRG
= V
BATSEL
= V
RELRN
= 5.5V
2.1
0.1
1
0.8
V
V
µA
SYMBOL
CONDITIONS
V
SOURCE
= 15V, V
PIN
= 13V to V
PIN
= 9V
MIN
TYP
0.3
MAX
0.88
UNITS
µs
V
SOURCE
= 15V, V
PIN
= 9V to V
PIN
= 13V
0.3
0.88
µs
4
_______________________________________________________________________________________
Power-Source Selector for
Dual-Battery Systems
ELECTRICAL CHARACTERISTICS
(V
BATA
= V
BATB
= V
CHGIN
= 16.8V, C
VDD
= 1µF, V
MINVA
= V
MINVB
= 0.93V, V
EXTLD
= V
ADPIN
= 28V, V
CHRG
= V
BATSEL
= V
RELRN
= 0,
C
ADPPWR
= C
REVBLK
= C
ADPBLK
= C
DISBAT
= C
DISA
= C
DISB
= C
CHGA
= C
CHGB
= 4.7nF,
TA = -40°C to +85°C,
unless otherwise noted.)
(Note 2)
PARAMETER
ADPIN, EXTLD Supply Voltage
Range
CHGIN, BATA, BATB, and
BATSUP Supply Voltage Range
V
ADPIN
= highest,
V
ADPPWR
= high
V
BATA
= 4.75V to 19V,
V
BATB
= 4.75V to 19V,
V
BATSUP
= 4.75V to 19V,
V
ADPIN
= 4.75V to 28V,
no external load at V
DD
V
ADPIN
= highest,
V
ADPPWR
= low
V
BATA
= highest, V
DISA
= high
V
BATA
= highest, V
DISA
= low
V
BATB
= highest, V
DISB
= high
V
BATB
= highest, V
DISB
= low
V
BATSUP
= highest
ADPIN Quiescent Current (ADPIN
Current When Not the Highest
Voltage)
BATA Quiescent Current (BATA
Current When Not the Highest
Voltage)
BATB Quiescent Current (BATB
Current When Not the Highest
Voltage)
EXTLD Quiescent Current
V
ADPIN
= 4.75V to 18V,
no external load at V
DD
V
BATA
= 4.75V to 19V,
no external load at V
DD
V
BATB
= 4.75V to 19V,
no external load at V
DD
V
ADPPWR
= high
V
ADPPWR
= low
V
DISA
= high
V
DISA
= low
V
DISB
= high
V
DISB
= low
CONDITIONS
MIN
4.75
4.75
MAX
28.00
19.00
50
54
42
50
42
50
40
1
µA
9
7.5
µA
16
7.5
µA
16
9.5
1.0
1.5
10
18.5
µA
µA
µA
UNITS
V
V
MAX1538
ADPIN, BATA, BATB, BATSUP
Quiescent Current (Current from
the Highest Voltage Supply)
Adapter selected (REVBLK or ADPBLK pins low)
Adapter not selected (REVBLK and ADPBLK pins high)
AC or airline state (CHGA, CHGB, and DISBAT pins high)
Charge state (CHGA or CHGB pin low, DISBAT pin high)
Discharge or relearn state (CHGA or CHGB pin low,
DISBAT pin low)
CHGIN Quiescent Current
LINEAR REGULATOR
V
DD
Output Voltage
V
DD
Undervoltage Lockout
COMPARATORS
ACDET, AIRDET Input Voltage
Range
ACDET, AIRDET Trip Threshold
MINV_ Operating Voltage Range
BAT_ Minimum Voltage Trip
Threshold
V
MINV_
= 0.93V
V
BAT_
falling
V
MINV_
= 1.5V
V
MINV_
= 2.6V
Input falling
0
1.94
0.93
4.59
7.4
12.86
5.5
2.06
2.60
4.72
7.6
13.14
V
V
V
V
I
VDD
= 0 to 100µA
Rising edge, relative to regulation point
3.270
-60
3.330
-10
V
mV
_______________________________________________________________________________________
5
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